It seems clear you are not getting what you need from your husband. However adding a second partner to fill a pot hole in a troubled marriage rarely works. And especially if the spouse is unaware there is even a problem...or oblivious to your needs.

How bad do you want to be married (to husband)?

Get the Love Languages book by Gary Chapman ...read it ...get him to read it. Discuss it with each other. Start there .. that's cheap ....I think you should consider marriage counseling. And I'd also cool things down with the roommate until some of these important marriage issues get discussed and worked on so clearer head can prevail.

I completely agree that you are not having your relationship needs met. I further agree that open and honest communication with your husband is critical at this point and that you will likely benefit from couples counseling.

I would like to add one thing to what dingedheart has said though. If you truly love and care about your husband, I would strike cheating on him off your option list. In my opinion, there is nothing more destructive to a relationship than lying, especially when it comes to involving others emotionally as well as sexually.